Pre-shipment inspection is the last process of inspection work in the factory. If the product has problems, it would be the last chance to correct at the factory. Substandard-product-caused economy and good will lost can be avoided by Pre-shipment inspection. Our random sampling inspection can reflect the actual situation that product appeared in different periods and different production line. Although this work cannot ensure qualified products in 100%, our report would reflect the proportion of defective products. Based on AQL, we can know whether the defect proportion of those products satisfies the standard in quality system.